/*
 * JBoss, Home of Professional Open Source
 * Copyright 2011, Red Hat, Inc. and individual contributors
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.mobicents.protocols.ss7.m3ua.impl.parameter;

import java.nio.ByteBuffer;

import org.mobicents.protocols.ss7.m3ua.parameter.Parameter;

/**
 * @author amit bhayani
 * @author kulikov
 */
public abstract class ParameterImpl implements Parameter {

	protected volatile short tag;
	protected volatile short length;

	public short getTag() {
		return tag;
	}

	protected abstract byte[] getValue();

	// public void encode(OutputStream out) throws IOException {
	// // obtain encoded value
	// byte[] value = getValue();
	//
	// // encode tag
	// out.write((byte) (tag >> 8));
	// out.write((byte) (tag));
	//
	// // encode length including value, tag and length field itself
	// length = (short) (value.length + 4);
	//
	// out.write((byte) (length >> 8));
	// out.write((byte) (length));
	//
	// // encode value
	// out.write(value);
	// }

	public void write(ByteBuffer buffer) {
		// obtain encoded value
		byte[] value = getValue();
		
		// encode tag
		buffer.put((byte) (tag >> 8));
		buffer.put((byte) (tag));

		// encode length including value, tag and length field itself
		length = (short) (value.length + 4);

		buffer.put((byte) (length >> 8));
		buffer.put((byte) (length));

		// encode value
		buffer.put(value);

		/*
		 * The total length of a parameter (including Tag, Parameter Length, and
		 * Value fields) MUST be a multiple of 4 octets. If the length of the
		 * parameter is not a multiple of 4 octets, the sender pads the
		 * Parameter at the end (i.e., after the Parameter Value field) with all
		 * zero octets. The length of the padding is NOT included in the
		 * parameter length field. A sender MUST NOT pad with more than 3
		 * octets. The receiver MUST ignore the padding octets.
		 */
		int remainder = (4 - length % 4);
		if (remainder < 4) {
			while (remainder > 0) {
				buffer.put((byte) 0x00);
				remainder--;
			}
		}
	}

}
